1. Field of the Invention
The present invention relates to a white balance correcting method and image-pickup apparatus, and more specifically to a technique for performing optimal white balance correction in flash photography.
2. Description of the Related Art
The flash-photographed image (hereinafter referred to as “main emitted image”) has different illuminating light sources for a main subject and a background (a main subject=ambient light+flash light, a background=ambient light). That hinders appropriate white balance correction.
The ambient light illuminating the main subject in flash photographing has stronger effect on the whole image in recent years as digital cameras have had higher sensitivity. If white balance correction is performed with a white balance gain (hereinafter referred to as “flash gain”) for each color of R, G, B, which are preset in correspondence with light source colors of the flash, with those digital cameras, colors on the main subject are badly affected.
For the purpose of solving the problems, an image processing apparatus described in Japanese Patent Application Laid-Open No. 2003-283918 is adapted to obtain a ratio of the amount of flash light to outside light to control white balance of an image that is flash-photographed based on the amount of light ratio.
A digital camera described in Japanese Patent Application Laid-Open No. 2003-309854 is adapted to obtain the final white balance gain by causing a flash to emit previously (pre-emit) to the main photographing, comparing a brightness value of a subject of a pre-emitted image obtained in the pre-emitting and a brightness value of a subject of a non-pre-emitted image obtained in the non-pre-emitting, obtaining the amount of the brightness value of a subject changed by the pre-emission and effect of the pre-emission on the brightness value of a subject, and performing weighting-adding on the flash gain and the white balance gain for the ambient light (stationary light) based on both of the values.